Method for producing a metallic container or can

ABSTRACT

A metal blank or tin plate is drawn to form a cup, said cup is then subjected to ironing, trimming and flanging to produce a metallic container or can. However the final ironing is not effected at all on the upper part of the can body wall. For this purpose, a punch core is used which has the upper portion of smaller diameter and the rest portion of larger diameter, the latter constituting a substantial part of the core. The container thus produced has a thin walled center portion constituting a greater part of the body wall and a thick walled upper portion constituting a smaller part of the body wall.

Yoshikawa METHOD FOR PRODUCING A METALLIC CONTAINER OR CAN [451Jan.15,1974

FOREIGN PATENTS OR APPLICATIONS Primary Examiner-Charles W. LanhamAssistant Examiner-M. J. Keenan Attorney-Watson, Leavenworth & Kelton[57] ABSTRACT A metal blank or tin plate is drawn to form a cup, saidcup is then subjected to ironing, trimming and flanging to produce ametallic container or can. However the final ironing is not effected atall on the upper part of the can body wall. For this purpose, a punchcore is used which has the upper portion of smaller diameter and therest portion of larger diameter, the latter constituting a substantialpart of the core. The container thus produced has a thin walled centerportion constituting a greater part of the body wall and a thick walledupper portion constituting a smaller part of the body wall.

1 Claim, 4 Drawing Figures [75] Inventor: Tatsumi Yoshikawa, Tokyo,Japan [73] Assignee: Daiwa Can Co., Ltd., Tokyo, Japan [22] Filed: May26, 1971 [21] Appl. No.: 147,073

[30] Foreign Application Priority Data June 4, 1970 Japan 45/54468 [52]US. Cl. 113/120 H, 72/348 [51] Int. Cl B21d 22/30 [58] Field of Search72/348; 113/120 H [56] References Cited UNITED STATES PATENTS 3,406,55410/1968 Frankenberg 72/348 3,029,507 4/1962 Gaggini 72/348 1,295,4302/1919 Carlson 72/348 3,556,032 l/1971 Fraze 113/120 H 1,944,527 1/1934Pfaendler 72/367 2,980,993 4/1961 Lyon 72/348 1 l A l ,i

PATENTEDJAH 15 I974 FIG. 2a

FIG. 2b

FIG.3

METHOD FOR PRODUCING A METALLIC CONTAINER OR CAN BACKGROUND OF THEINVENTION It is known that a metal blank or tin plate is drawn to form acup, which is then subjected to ironing to form an incomplete tubularcan with an end, thereafter it is stripped off the punch core, and theupper zig-zag part of said cup is trimmed, then a part of the trimmedupper part is subjected to flanging and double seaming with a cover toform a can. In order to keep costs down, it has been a desideratum tomake the body wall of the can as thin as possible and to elevate the canmaking speed as high as possible. On the other hand, however, it hasbeen considered to be impossible to fulfil the above two items for thefollowing reason.

The cup as formed by drawing does not have the same thickness all aroundthe body wall. Thus, when the cup is subjected to ironing, the thickportion is elongated more than the thin portion, which results in thatthe upper edge of the body wall is rendered zigzag. As the can isstripped off the punch core after completion of ironing, the outermostprojected tip ofsaid zigzag portion butts first against the finger ofthe stripper. If the outermost projected tip has a substantial thicknessand/or the depth of said zig-zag portion is shallow, it will not be benteven when it butts against the finger of the stripper at a high speed.If said tip is thin, however, it will be bent unless it butts againstthe finger of the stripper at a low speed.

It has been thought that when the punch core is stripped of the canafter ironing, the punch core should take an inverted truncated conicalform having a greater diameter in the upper part or a cylindrical formhaving substantially identical thickness throughout the vertical length.The can body which has been subjected to ironing by the use of a punchcore in the form of an inverted truncated cone has a wall thicker in thelower part and thinner in the upper part. When a punch core in acylindrical form is used for ironing of the can body, it has a wallhaving the same thickness throughout the vertical length. In any case,when it is intended to make the can wall thin to decrease the amount ofmaterial to be used for the can, the upper end of the body wall becomesso thin that it will easily be bent when the core is stripped.

In this invention, the upper part of the can body wall is so thick and azig-zag portion of said part is so shallow that it will not be bent evenwhen it butts against the finger of the stripper at a productionvelocity of at least 200 cans per minute. The central part of the canbody wall has a very small thickness after ironing. The punch core usedin this invention is such that it will produce the above structure ofthe can body wall.

U.S. Pat. No. 3,029,507 indicates that a disc made of aluminum is formedinto a tubular can with an end, which is then subjected to ironing so asto elongate the body wall thinly. A can formed by impact extrusion asshown in said U.S. Patent has the same wall thickness with respect to asection perpendicular to the axis of the can, as is different from a canmade by drawing. Thus the can made by impact extrusion will hardlyproduce any zigzag portion in the upper body edge after ironing of saidbody wall, and there are fewer cases of being bent by the stripperfinger than with the can made by drawing when the thickness of the upperend is equal. Accordingly there is no consideration in said U.S. Patentabout the zigzag problem of the upper edge of the can, and thus nodescription therein about a technical idea of imparting little or noironing upon the upper part of the can body in the last step, which willdistinguish the present invention from that shown in said U.S. Patent.

SUMMARY OF THE INVENTION This invention relates to a method forproducing a metallic container or can with the upper edge of the bodywall having a thickness enough to maintain its original form even whenit butts against the stripper finger at high speed. For the purpose, thefinal ironing is not effected on the upper part of the product after thefirst ironing. Thus the finished product has a thin walled centerportion constituting a greater part of the body wall and a thick walledupper portion constituting a smaller part of the body wall.

It is another object of the invention to provide a can with a thickwalled upper edge of the can having such thickness as not to be benteven when it butts against the finger of the stripper, the other partthan the upper edge of said can having an extremely thin thickness so asto curtail the amount of material to be used for the can.

It is a further object of the invention to provide a can which has beensubjected to drawing, ironing, trimming and flanging and which has inthe upper part a thickness enough to double seam a metal end thereupon,while in the other part an extremely thin thickness.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a sectional view out along aplane containing an axis of a tubular can of this invention.

FIG. 2a is a vertical sectional view of a cup as formed by drawing.

FIG. 2b is a vertical sectional view of a cup of FIG. 2a after the firstironing.

FIG. 3 is a front view of a punch core of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The word drawing used herein ismeant by a process in which a circular metal blank or tin plate is heldunder suitable pressure between a die plate and a pressure plate, saidplate is then caused to pass with a punch core drawing die ring, and acup is formed thereby. In this case, the difference between the outsidediameter of said punch core and the inside diameter of said die ringbeing at least twice the thickness of the tin plate.

The word ironing used herein is meant by a process in which the wall ofthe cup body is thinly elongated when the cup is caused to pass with thepunch core through an ironing die ring since the difference between theoutside diameter of the punch core and the inside diameter of theironing die ring is less than twice the thickness of the wall of the cupbody.

A cup A shown in FIG. 2a is one as formed by the above drawing. Thebottom end wall thickness is substantially equal to that of a tin plate.The body wall thickness is nearly equal to that of the tin plate, butdoes not have the same thickness for the reasons that the pressure forholding the tin plate does not substantially uniformly act upon the tinplate, that the tin plate itself does not have the uniform thickness andthat the material of the tin plate is not uniform, etc. This cup A issubjected to ironing by the use ofa punch core shown in FIG. 3 (theironing die ring used is not shown). The punch core shown in FIG. 3 hasa lower zone 4? in the lower part thereof which is progressivelyenlarged in upward direction, a central zone which rests on the zone 4Pand has an equal diameter, an upper zone 9 which rests thereon and hasprogressively smaller diameters in upward direction and an uppermostzone thereon having a small diameter. As the cup is caused to pass withthe punch core through the ironing die ring, the part of the cup whichhas contacted the zone 4P of the punch core is shown as 4a in FIG. 2bshowing a product after the first ironing is over. It is the lower partof the body wall of the cup having a thickness which is progressivelysmaller in upward direction. The central part 511 and the upper part 6ain FIG. 2b are those having contacted the central zone of the punch corewith an equal diameter. Therefore, an open end of said product remainswithin the central zone.

As set forth hereinabove, since the wall of the cup body does not havethe same thickness, the elongation by the above stated ironing of thebody wall is not uniform with respect to the entire circumferencethereof. Accordingly, the open end of the body wall will become zigzagas indicated by the reference numeral 8 in FIG. 2b. The open end of thebody wall after the first ironing is positioned below the upper zone 9of the punch core. When the final ironing is effected to the product asshown in FIG. 2b which has been subjected to the first ironing, thecentral part of the body wall of the product is thinly elongatedsuccessively from the lower part 4a thereof and the upper part 6aincluding the open end of the product will reach within the uppermostzone of the punch core. In this ironing step, the rate of reduction ofthe thickness in the part 6a will not occur at all. After this producthas been past through the final ironing die ring, it is stripped off thepunch core. The product after the final ironing subjected to trimming isshown in FIG. 1. As compared with the product of FIG. 2b, the can shownin FIG. I has the bottom end 2 made concave internally, the parts 4 andmade thinner then the parts 4a and 5a and the upper part 6 not madethinner, than the part 6a. Thus the depth of the zig-zag portion of theupper part of this product is not deeper than that of the product ofFIG. 2b. In FIG. 1, the part 7 represented by a dotted line shows anoutwardly, radially bent portion by flanging of the upper edge of thepart 6 after trimming. In the can in FIG. 1, the bottom end 2 has thesame thickness as that of the tin plate and the arc plate 3 connectingthe end 2 with the body wall has the thickness extremely slightlysmaller than that of the tin plate. The lower part 4 has theprogressively smaller thickness in upward direction and the successivecentral part 5 constituting a greater part of the body wall has thesmallest thickness. The successive part thereon is made progressivelythicker which leads to the uppermost part having such thickness as notto be bent when it butts against the finger of the stripper. Examples ofthickness of each part are 0.35 to 0.30 mm for the end 2 and the arepart 3, 0.30 to 0.10 mm for 10 mm of the lower part 4, about 0.10 mm forthe central part5, 0.10 to 0.20 mm for about 5 mm of the upper part 6and about 0.20 mm for the upper edge of the body wall.

The can was made of tin plate but other material such as aluminum can beused. The rate of production was 250 cans per minutes but there wassubstantially no bending of the upper edge of the can. For the purposeof double seaming, it is preferable to have the upper part with thethickness of 0.2 mm extended in 5 mm or so below the upper edge aftertrimming.

The above description is only one embodiment of the invention. Afterdrawing, the ironing can be effected once or several times. In any caseit is possible to produce a can in which the upper part of the body wallhas the thickness greater than that of the central part thereof asshown.

The thickness of the tin plate, the rate of reduction of the thicknessof the lower part 4 of the body wall and the rate of increase of thethickness of the upper part 6 may vary with the material used and notconfined to the figures used the above examples. However, since it is anobject of the invention to reduce the amount of material used, it isobviously desirable to made the central body wall as thin as possible bysharply decreasing or increasing in drawing or ironing the thickness ofthe other parts of the body wall without destroying thereof. Thethickness of the central part may thus be made 0.1 mm or less. When thethickness of the upper edge of the body wall is 0.18 to 0.28 mmaccording to the particular material used, it is not bent as it buttsagainst the stripper finger even at the production rate of 250 cans/-min and a metal cover can be double seamed by the use of an ordinarydouble seamer. When the second ironing or the subsequent ironings areconducted by means of the punch core, the omission of ironing of theupper part of the body wall in the last ironing will result in fewerzigzag portions of the upper edge. This is because the thickness of thebody wall is made equal after the first ironing with respect to a planeperpendicular to the axis of the can and thus the zigzag portion of theupper edge resulting from the first ironing will not be exaggerated anylonger so long as it is not elongated. For the reason above, there isfew distances in this invention between the projected part and therecessed part in the zigzag portion of the upper edge of the wall of thecan body, which will cause advantages of preventing the projected partfrom bending as it butts against the finger of the stripper.

It is thought that the invention and its attendant advantages will beunderstood from the foregoing description and it will be apparent thatvarious changes and modifications may be made without departing from thespirit and scope of the invention.

I claim:

1. A method for producing a metallic container comprising drawing ametal blank to form therefrom a cup which includes a bottom wall and aside wall extending upwardly from said bottom wall and terminating in anopening at the top of said cup, said cup bottom wall and side wallhaving substantially the same thickness,

providing an elongated punch core having an end segment whichprogressively enlarges in diameter in the direction of its other end andwhich merges with a second segment of substantially uniform diameter, athird segment adjacent said second segment and having progressivelysmaller diameter in the direction of said other end, and a fourthsegment adjacent said third segment and having a substantially uniformdiameter not larger than the smallest diameter of said third segment,

6 positioning said core punch vertically with said end location in saidcore punch second segment,

segment at the bottom and receiving said core then effecting the furtherironing of said product by punch in said cup through said opening,elongating the central part of the body wall without then effecting afirst ironing of said cup with said elongating the upper portion thereofand while punch core by elongating the body wall including 5 maintainingsaid cup opening positioned at a locathe upper part thereof and reducingthe thickness tion in the fourth zone of said punch core, and of thelower part of the body wall in a degree in then stripping the containeroff the punch core and which said thickness becomes progressivelysmaller thereafter effecting trimming and flanging the end in adirection upward from said bottom wall, and of the container. whilemaintaining said cup opening positioned at a 10

1. A method for producing a metallic container comprising drawing ametal blank to form therefrom a cup which includes a bottom wall and aside wall extending upwardly from said bottom wall and terminating in anopening at the top of said cup, said cup bottom wall and side wallhaving substantially the same thickness, providing an elongated punchcore having an end segment which progressively enlarges in diameter inthe direction of its other end and which merges with a second segment ofsubstantially uniform diameter, a third segment adjacent said secondsegment and having progressively smaller diameter in the direction ofsaid other end, and a fourth segment adjacent said third segment andhaving a substantially uniform diameter not larger than the smallestdiameter of said third segment, positioning said core punch verticallywith said end segment at the bottom and receiving said core punch insaid cup through said opening, then effecting a first ironing of saidcup with said punch core by elongating the body wall including the upperpart thereof and reducing the thickness of the lower part of the bodywall in a degree in which said thickness becomes progressively smallerin a direction upward from said bottom wall, and while maintaining saidcup opening positioned at a location in said core punch second segment,then effecting the further ironing of said product by elongating thecentral part of the body wall without elongating the upper portionthereof and while maintaining said cup opening positioned at a locationin the fourth zone of said punch core, and then stripping the containeroff the punch core and thereafter effecting trimming and flanging theeNd of the container.